1,720,965 research outputs found
Evolutionary trends and patterns in centipedesegment number based on a cladistic analysis ofMecistocephalidae (Chilopoda: Geophilomorpha)
No full textEvolutionary changes in segment number during the radiation of
Mecistocephalidae, a group of geophilomorph centipedes with segment number
usually invariant at the species level, were explored based on a cladistic analysis of
forty-six mecistocephalid species, representative of the extant diversity in segment
number. The data matrix included 118 morphological characters. Trends were
recognized in the evolution of segment number and discussed in relation to the
underlying ontogenetic mechanisms of segmentation. The basic trend was towards
an increasingly higher number of leg-bearing segments, from (most probably)
forty-one to sixty-five (101 in one exceptional case). Changes always involved
even sets of segments. Additions of two, four or eight segments usually occurred,
but a case of overall duplication of the whole number was also documented. Most
changes occurred starting from values belonging to the arithmetical series fortyone,
forty-five, forty-nine, whereas the intermediate values forty-three, fortyseven,
fifty-one were often evolutionary dead-ends. This evidence suggests a
multiplicative mechanism of segmentation involving one or more final run of
duplication, as well as a precise control of the final number of segments which
produces absolute number stability, except for a single, highly derived species with
an exceptionally high number of segments. These ideas contribute to a more
general model of arthropod segmentation recently developed by Minelli. A taxonomic
revision of mecistocephalids is presented: three subfamilies are proposed
(Arrupinae, Dicellophilinae and Mecistocephalinae) and Sundarrup is recognized
as a junior synonym of Anarrup
A new mecistocephalid centipede from Ryukyu Islands and a revisitation of ̃Taiwanella" (Chilopoda: Geophilomorpha: Mecistocephalidae)
No full textProterotaiwanella tanabei n. g. n. sp. is described for a mecistocephalid centipede collected in
Kume Island, Ryukyu Archipelago, Japan. Of the two Taiwanese species originally included in the
genus ‘Taiwanella’ Takakuwa, 1936 (invalid name), ‘Taiwanella’ sculptulata Takakuwa, 1936 is
recognised as belonging to the new genus (as Proterotaiwanella sculptulata (Takakuwa, 1936), n.
comb.) while ‘Taiwanella’ yanagiharai Takakuwa, 1936 is recognised as belonging to the large
genus Mecistocephalus Newport, 1843 (as Mecistocephalus yanagiharai (Takakuwa, 1936), n.
comb.). The geographical range of the two species of Proterotaiwanella (Taiwan and Ryukyu
Islands) parallels a distribution pattern common to some mecistocephalid taxa
Increase by duplication and loss ofinvariance of segment number in thecentipede Mecistocephalus microporus(Chilopoda, Geophilomorpha,Mecistocephalidae)
No full textIntraspecific variability in the number of trunk segments is
demonstrated for the first time in a representative of the Mecistocephalidae,
a basal clade within the geophilomorph centipedes.
This destabilization of an otherwise species-constant segment
number is interpreted as a result of the recent quasi-duplication of
segments shown by Mecistocephalus microporus Haase, 1887, with
respect to its most recent ancestor. The new finding fits well with
a recently proposed biphasic model of centipede segmentation.
The species is redescribed and two new synonymies are proposed:
Megethmus Cook, 1895 as junior synonym of Mecistocephalus
Newport, 1843 and Megethmus pluripes Chamberlin, 1920
as a junior synonym of Mecistocephalus microporus Haase, 1887
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Phylogeny and systematics of the Arrupinae (Chilopoda Geophilomorpha Mecistocephalidae) with the description of a new dwarfed species
No full textF. 28. Total body length in Arrupinae plotted on a simplified phylogeny in accordance with the cladistic analysis presented above. Maximum and minimum values of adult body length (in mm) are given for each genus.Published as part of FODDAI, DONATELLA, BONATO, LUCIO, PEREIRA, LUIS ALBERTO & MINELLI, ALESSANDRO, 2003, Phylogeny and systematics of the Arrupinae (Chilopoda Geophilomorpha Mecistocephalidae) with the description of a new dwarfed species, pp. 1247-1267 in Journal of Natural History 37 (10) on page 1263, DOI: 10.1080/00222930210121672, http://zenodo.org/record/526006
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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